Oven for drying metal sheets



Dec 28, 1943.

ITIFFH H m TITIFH'II II 1L 4 JUITFTZ Filed Nov; 12, 1.941

J. COYLE OVEN FOR DRYING METAL SHEETS 4 Sheets-Sheet l Dec. 28, 1943. J. COYLE I OVEN FOR DRYING METAL SHEETS 4 Sheets-Sheet 2 Filed Nov. 12, 1941 Dec. 28, 1943. J. COYLE OVEN FOR DRYING METAL SHEETS 4 Sheets-Sheet 3 Filed Nov. 12, 1941 Dec. 28, 1943. J. COYLE 2,337,649

OVEN FOR DRYING METAL SHEETS Filed Nov. 12, 1941 4 Sheets-Sheet 4 fun/5 r Patented Dec. 28, 1943 OVEN FOR DRYING METAL SHEETS John Coyle, Baltimore, Md., assignor to Continental Can Company, Inc., New York, N. Y., a corporation of New York Application November 12, 1941, Serial No. 418,864

4 Claims.

The invention relates to new and useful improvements in an oven for drying and/or baking freshly printed, lacquered or varnished sheet metal plates and more particularly to the means for circulating heated across across the sheets during the drying and baking operation.

An object of the invention is to provide a means for rapidly circulating the drying air in continuous successive cycles across the sheets from one side thereof to the other by means which not only forcibly discharge air into the oven at one side thereof, but also draw the air out of the oven at the opposite side thereof.

A further object of the invention is to provide an air circulating system of the above type wherein a unit of drying air in one cycle of movement crosses the sheet at one level and in the next cycle of movement crosses the sheet at another level, so as to ensure a uniformity in the temperature and condition of the drying air throughout all the regions of the sheet.

A still further object of the invention is to provide an air circulating system of the above type with means for drawing off a limited portion of the circulating air and means for replenishing the flowing stream with fresh heated air.

A still further object of the invention is to provide means which may be utilized from time to time for determining the rate at which the circulating drying air becomes foul through absorption of the volatiles driven off during the treating of the sheets.

In the drawings which show by way of illustion one embodiment of the invention:

Figure l is a side View showing more or less diagrammatically an oven for drying and/or baking the metal sheets which oven is equipped with the improved air circulating units.

' Figure 2 is a plan view of a portion of the oven and one of the air circulating units.

Figure 3 is a side View on an enlarged scale of a portion of the oven and one of the air circulating units showing in full lines the ducts and ports for discharging air into the oven and in broken lines the ducts and ports for drawing air from the oven and returning the same to the circulatmg means.

Figure 4 is a view in side elevation of a portion of the oven and one of the air circulating units taken from the side of the oven where the air is exhausted and showing the ducts for returning the air to the circulating devices therefor, one of the circulating devices being broken away to show the multivane rotor.

Figure 5 is a vertical sectional view through the oven showing more or less diagrammatically the conveyors for the sheets, the sheets which are being dried, the heating means for the oven and the air ducts and ports for discharging air into the oven at one side and for drawing the air out of the oven at the opposite side of the sheet.

The oven to which the improvements apply is adapted for drying or baking freshly printed, lacquered or varnished sheet metal plates. The oven construction generally, including the conveyor for the sheets and the heating means, may be of any desired construction. The novel features of the present invention have to do with the air circulating system for moving air in continuous successive cycles across the sheet from one side thereof to the other by means which push the air into the oven through ports at one side and pull the air from the oven through opposed ports at the other side. This causes the air to flow rapidly across the sheet from one side thereof to the other.

In each circulating system are two multivane air transfer devices, one of which at the delivery side is connected through ducts with ports substantially on the line of travel of the upper half of the sheets pasisng through the oven, while the delivery side of the other air transfer device is connected to and discharges air through ducts with a series of ports substantially on the line of travel of the lower half of the sheets. There are similarly disposed lines of ports on the opposite side of the oven and the upper series of ports is connected to the intake side of the second mentioned air transfer device, while the lower series of ports is connected through ducts with the intake side of the first mentioned air transfer device. This causes the air to circulate in continuous successive cycles and a unit of the air to pass across the lower half thereof and then across the sheet in the upper half thereof and so on.

In order to maintain the circulating air in an efficient condition for absorbing the volatiles, adjustable means is provided for taking off a limited portion of the circulating air and also for replenishing the air stream with fresh air.

Referring more in detail to the drawings, the improved oven consists of suitable insulated side members I and 2 connected by an insulated top member 3. There is also a suitable bottom closure member A. This provides an elongated chamber having an entrance end and an exit end through which chamber the sheets are conveyed baking chamber in what might be called a line of travel free from contact with the side walls of the oven.

There is a series of air circulating units indicated at 5,1,8,9, i9, II and in Figure 1 of the drawings. These units are independent of each other as to the air circulating means and also discharged or pushed into the drying chamber through the ports 32 to 36 will cross the upper half of the sheets and will be pulled into the ports id to 48 and thence directed into the conduit 50 and to the intake side of the air transfer device A.

Following a unit of drying air after it reaches the air transfer device A, it will be passed into the drying chamber, across the lower half of the travelling sheets, thence into the conduit 42 and to the intake side of the air transfer device B. From the air transfer device B, this unit of circulating air will be delivered to one of the ports 32 to 36 into the drying chamber and across the upper half of the travelling sheets and thence into the conduit 49 and to the intake side of the as to the heating means associated therewith and the description of one will answer for the others.

Each heating unit includes two multivane air transfer devices. A portion of the rotor of one of the units is shown in Figure 4. This rotor A includes radially extending vanes. The air to be transferred is received within the rotor and is discharged by these vanes at the periphery thereof. As noted above, there are two air transfer devices in each unit and these air transfer devices have been lettered A and B respectively. The rotors of the air transfer devices are driven from a motor M by suitable belts I3 and 14, the belt l3 driving the air transfer device B and the belt I 4 driving the air transfer device A. See Figure l.

. Associated with the air transfer device A is a conduit l5 having branches I6, I1, l8, l9 and which are connected respectively with ports 2|, 22, 23,-24 and 25. These ports extend through the'side wall I of the oven as shown in Figure 5. These ports 2| to 25 through which air is discharged into the drying chamber are substantially on a line with the path of travel of the lower half of the sheets S.

Associated with the air transfer device B is a conduit 26 having branches 21, 28, 29, 30 and 3! which are connected respectively with ports 32, 33,3 i, and 36. These ports 32 to 36 through which air is discharged into the drying chamber from the air transfer device B are substantially on a line with the path of travel of the upper half of the sheets S.

In the opposite wall 2 of the oven there is a series of ports 31, 38, 39, All and M which are directly opposed to the ports 2| to 25 respectively. These ports 3'! to M are connected with branchconduits leading to a main conduit 52 and this main conduit 12 is connected to a conduit A3 which extends across the oven, over the top of the same and in turn is connected to the intake sideof the air transfer device B.

From-the above it would be apparent that air branch conduits to a main conduit 49 which in turn is connected to a conduit 58 extending across the oven above the top thereof and this conduit 58 is'connected to the intake side of the air transfer device A.

From the above it will be apparent that air air transfer device A.

The air therefore circulates in cycles into the drying chamber, out of the drying chamber, back to the air transfer device and thence again through the drying chamber. With these multivane air transfer devices, the air is pushed into the drying chamber and pulled therefrom at the opposite side so that it moves very rapidly across the sheet. With the arrangement described above, a unit of the drying air will pass across the sheet at one level and then across the sheet at another level, alternating so that the air crossing the sheets will be so distributed and intermixed in its crossing that the air will be of substantially uniform condition and temperature throughout all of the regions of the sheet. In other words, the air crossing the lower portion of the sheet will be of substantially the same temperature as the air crossing the upper portion of the sheet.

With this multivane type of air transfer device,

the air may be circulated very rapidly, as for example in the neighborhood of 500 feet per minute, so that a unit of drying air will pass through the multivane impeller at something like 20 times per minute. This rapid movement of the air ensures a uniformity of condition of the air and a substantial uniformity of the temperature of the drying air. Furthermore the rapid movement of P the air across the sheets will perform more or less of a scrubbing action, removing the gas-like fume clinging to the drying surface so that the coating on the sheet will be more quickly dried and set.

Any suitable heating means may be used in connection with the oven. In Figure 5 burners 5| are illustrated. Whatever the heating means may be, it is desirable that the heating devices associated with the several air circulating units shall be independent to the extent that one air circulating unit may be subjected to a higher range of temperature than the others. When the sheet enters the oven, it is usually cold and likewise the conveyor iscold, and it is desirable to employ a greater heating temperature in connection with the circulating unit adjacent the entrance end. Also as the sheet enters this first unit, it is more or less wet from the application of the enamels or lacquers. After the sheets are raised to oven temperature, then a lesser heat is applied to the air circulating unit. Through the regulating of the heating units associated with the several air circulating units, a proper degree of temperature may be maintained throughout the entire oven for most efficiently and quickly drying and baking the sheets without injuring the same.

In order to maintain the circulating air in an efficient condition for absorbin the volatiles, the air ducts t2 and 49 are each provided with a stack shown at 52 and 53 respectively. In each stack is;

a damper 54 to which an arm 55 isconnected and this arm is adjustably clamped to a bracket 56 by any suitable device so that the setting of the damper may be adjusted. This damper is preferably set so as to permit a limited portion of the drying air moving in the cycle to escape. Heated air comin up around the burners will pass into the flowing stream and replenish the same so as to maintain a proper volume of flowing air for drying and conditioning the sheets.

As a means for testing the condition of the circulating air, each of the ducts 42 to $9 is provided with an opening through which testing screens may be inserted. One of the screens is indicated at 51. This screen is in the nature of a slide which slides through the opening in the conduit which may be opened and closed in any suitable way and, when placed across the conduit, the circulating air passes through the screen. This screen may be of finely woven fahric or closely-placed strings of fibrous material to which the volatiles carried in suspension in the air would cling.

The screen is placed in the conduit and inspected from time to time and thus the period re- L quired for causing the screen. to become foul. is determined. From this it can be readily determined whether this period is too short or too long for the eificient operation of the oven. If it is found to be too short, then the damper can be adjusted so as to permit more of the flowing air to escape which will cause fresh air to enter the flowing stream. On the other hand, if the period of time before the screen becomes foul is longer than the normal, fixed period, then the damper should be adjusted so as to permit less of the circulating air to escape. It will be seen from the above that these tests will show the best conditions under which to operate each unit of the air circulating system.

It is not thought necessary to set forth in detail the operation of the improved drying and baking oven as the novel features have been pointed out above and the manner in which they operate. It may be stated in a general way that the sheets, after they are printed or lacquered or varnished, are placed on the conveyor adjacent the entrance end of the oven are carried into and through. the oven by this conveyor. The sheets are on edge and as they move through the oven, which is heated, air is circulated across the sheets for carrying ofi volatiles and for assisting in uniformly heating the By the use of these separate units which have been described, the entrance end of the oven may be maintained at a higher heat so as to quickly bring the sheets to a temperature for the baking of the coating and the other units may be so adjusted that there will be no overheating of the coating during the baking operation.

It is obvious that many changes in the details of construction may be made not departing from the spirit of the invention as set forth in the appended claims.

I claim:

1. An oven construction for drying or baking sheet metal plates, comprising an elongated chamber having an entrance at one end an an exit at the other, a convey-or movable u the chamber for conveying the sheets therethrough in substantially vertical position, said chamber having a series of intake ports and directly opposed outlet ports in the side walls thereof and disposed along the path of travel of the upper portion of the sheets and a series of intake ports and directly opposed outlet ports in the side walls thereof disposed along the path of trave1 of the lower portion of the sheets, ducts connecting the lower outlet ports with the upper intake ports and ducts connecting the upper outlet ports with the lower intake ports wherebya unit of flowing air stream will be caused to cross the path at different levels in successive cycles, means located in the ducts for forcibly moving the air stream, means for removing from the flowing stream a limited portion of air and for replenishing the flowing stream with fresh air, and means for heating the chamber.

2. An oven construction for drying or baking sheet metal plates, comprising an elongated chamber having an entrance at one end and an exit at the other, a conveyor movable through the chamber for conveying the sheets therethrough in substantially vertical position, a series of independent air circulating units disposed along said chamber, each of said circulating units including a series of intake ports and directly opposed outlet ports in the side walls thereof disposed along the path of travel of the upper portion of the sheets and a series of intake ports and directly opposed outlet ports in the side walls thereof disposed along the path of travel of the lower portion of the sheets, a duct connecting the lower outlet ports with the upper intake ports and a duct connecting the upper outlet ports with the lower intake ports whereby a unit of the flowing air stream will be caused to cross the sheet at different levels in successive cycles, a multivane air propelling device located in each duct and means associated with each unit for heating the air circulating across the sheets.

3. An oven construction for drying or baking sheet metal plates, comprising an elongated chamber having an entrance at one end and an exit at the other, a conveyor movable through the chamber for conveying the sheets therethrough in substantially vertical position, a series of independent air circulating units disposed along said chamber, each of said circulating units including a series of intake ports and directly opposed outlet ports in the side walls thereof disposed along the path of travel of the upper portion of the sheets and a series of intake ports and directly opposed outlet ports in the side walls thereof disposed along the path of travel of the lower portion of the sheets, a. duct connecting the lower outlet ports with the upper intake ports and a duct connecting the upper outlet ports with the lower intake ports whereby a unit of the flowing air stream will be caused to cross the sheet at different levels in successive cycles, a multivane air propelling device located in each duct, means associated with each unit for heating the air circulating across the sheets and means for removing from the flowing stream a limited portion of air and for replenishing the flowing stream with fresh air.

4. An oven construction for drying or baking sheet metal plates, comprising an elongated chamber having an entrance at one end and an exit at the other, a conveyor movable through the chamber for conveying the sheets therethrough in substantially vertical position, a series of independent air circulating units disposed along said chamber each of said circulating units including a series of intake ports and directly opposed outlet ports in the side walls thereof disposed along the path of travel of the upper portion of the sheets and a series of intake ports and directly opposed outlet ports in the side walls thereof disposed along the path of travel of the lower portion of the sheets, a duct connecting the lower outlet ports With the upper intake ports and a duct connecting the upper outlet ports with the lower intake ports whereby a unit of the flowing air stream will be caused to cross the sheet at difierent levels in successive cycles, a multivane air propelling device located in each duct, means associated with each unit for heating the air circulating across the sheets, means for removing from the flowing stream a limited portion of air and for replenishing the flowing stream with fresh air, each unit including a test screen and means whereby the screen may be placed across the flowing stream for determinin the condition of the air stream.

JOHN COYLE. 

